1. Field of the Invention
The present invention relates to improvements in heat exchangers of the type wherein a first fluid is circulated through a cavity through which pass conduits carrying a second fluid, such that a heat exchange takes place between the two fluids. More particularly the invention relates to improvements in a heat exchanger wherein a core cavity is at least partly bounded by an arcuate wall such that the first fluid is directed in an arcuate path generally parallel to the arcuate wall.
2. State of the Prior Art
It is known to construct heat exchangers wherein a cylindrical cavity is defined within a container including a fluid inlet and a fluid outlet spaced circumferentially from each other on the cylindrical container wall. The cylindrical cavity of the prior art heat exchanger is partitioned into two equal semicylindrical compartments by a diametrically extending center baffle. The center baffle has two diametrically opposed edges, the upper one of which is joined to the cylindrical container wall between the inlet and the outlet. The fluid inlet and the fluid outlet conduits enter through a cylindrical wall into the heat exchanger cavity near the upper edge of the center baffle but on opposite sides thereof. The opposite, lower edge of the baffle is shaped to define an aperture between the two compartments so that fluid introduced into the first compartment through the inlet circulates in a generally arcuate path through the first compartment then passes to the second compartment through the aperture in the opposite edge of the baffle and continues through the second compartment, still in a generally arcuate path, finally exiting the core cavity through the outlet opening.
The housing of the prior art heat exchanger further includes two end walls which may be planar and parallel to each other to define a right cylinder. A number of relatively small diameter cooling tubes of a thermally conductive material, such as aluminium, extend through the core cavity between the end walls. A stream of fluid such as air may be circulated through the cooling tubes where it is brought into thermal contact with the fluid circulating through the core cavity, so that a thermal exchange takes place between the two fluids. In a particular heat exchanger construction known to the prior art, the inlet and outlet are circumferentially separated by a relatively small angle, e.g. less than forty five degrees. The fluid entering the core cavity through the inlet must therefore flow through a generally arcuate path in excess of 270 degrees before reaching the outlet. The fluid is directed in this arcuate path by the cylindrical peripheral wall.
It has been found that excessive fluid flow takes place close to the peripheral wall while the fluid in the central area of the core cavity is relatively stagnant. This is detrimental to the cooling efficiency of the heat exchanger because relatively little cooling or heat exchange takes place at or through the peripheral wall, which has a relatively small surface area compared to the aggregate surface of the cooling or heat exchange tubes extending through the core cavity.
It is also known to introduce "turbolator" elements into heat exchange tubing for the purpose of increasing the turbulence of the coolant fluid to thereby increase the heat transfer from the tubing to the coolant fluid. This occurs because fluid flowing through the center of the tube is directed against the tube walls where it absorbs heat. If the flow were not disturbed by the turbolator element the centrally flowing coolant fluid would be relatively insulated by the coolant fluid flowing adjacent to the tube walls.
Previously used turbolator elements known to the Applicant include coil springs positioned coaxially within the heat exchange tubing. While such structures brought about increased turbulence, the coil element also diminished the aperture of the tubing, partly obstructing fluid flow, and also encouraged eventual clogging of the tube because the coil tends to accumulate particulate matter carried by the coolant fluid.